1. Field of Invention
The present invention relates to systems for severing subterranean pipes and the like, and in particular to an apparatus and system designed to prevent or at least reduce the buildup of cutting gas and explosion of the same during the cutting of underwater abandoned wellheads and the like.
The present system as configured is primarily designed for use in conjunction with generally longitudinally arranged pipes, such as wellhead conductor pipe or the like, and teaches the use of an apparatus configured to slidingly envelope the pipe, having the capability for excavating the area immediately about the pipe such that the apparatus migrates about and down the pipe to a predetermined depth, flushing out the mud about the conductor pipe which sometimes traps cutting torch gas during cutting operations and causes explosions or the like.
The present preferred system utilizes a jetting arrangement for the excavation process, wherein there is provided a coupling system, a conduit system for conveying pressurized fluid such as water or the like, and a jetting system about the base of the apparatus for the jetting of the soil to the desired depth, and for circulating the pressurized fluid between the apparatus and the outer wall of the conductor pipe once the desired depth is reached and the cutting operation has begun.
2. Prior Art & General Background
Federal law requires that, in abandoning a subsea oil or gas wellhead, the conductor casing be removed to a depth of at least fifteen (15) feet below the mud line so that it does not pose a hinderance to navigation.
In accomplishing this task, divers often must climb into the casing itself to a depth of at least fifteen (15) feet below the mud line, and cut the casing, often utilizing an oxygen/arc cutting torch or like system. This operation is very risky in that gases created by the burning pipe metal combine with residual oxygen from the cutting process to form pockets of gas in the mud surrounding the cutting area. These pockets often ignite and explode, causing death or serious injury to the diver.
Until now, there has been no apparatus which would displace the mud from about the periphery of a subterranean pipe or the like and provide a circulating, fluid current for removing explosive residual gas from the cutting area, preventing gas build-up and the potential for explosion.
U.S. Pat. No. 4,900,198 to Hoaki describes a "Method and Apparatus for removing Old Pile", wherein (note FIG. 1) there is disclosed a "bucket" having a diameter apparently sufficient to slidingly envelope the pile to be removed, and further incorporating water jetting means (elements 19, 23, and 24) for displacing soil to allow the bucket to "travel" in longitudinal fashion down the pile under the mud line, so that it may cut the pile one section at a time for removal.
While the '198 patent is pertinent, it is nonetheless fully distinguishable from the present system, and in fact could not be used with the present system. Indeed, Hoaki teaches an apparatus for removing rotted wood piles or the like, and did not contemplate a system for extended excavation depths and circulation means to above the mud line for preventing explosive build-up of cutting gasses.
Thus, while the prior art may contemplate apparatus and systems for cutting pile and piping, none appear to teach or even suggest a system for providing an optimally safe environment for subterranean pipe removal operations utilizing cutting torches or the like.